Class booklet
Workshop 4 Light and focus
Tips & suggestions
1 Exercise your eye We recommend you attend a maximum number of photo exhibits and consult the works of the masters of photography on a regular basis. Exercising one’s eye is one way to progress. It helps you recognize your tastes and helps the composition of your images as you move forward.
2 Continue You will follow the photography initiation training for beginners. We think that you could enjoy the thematic courses as a logical follow-up to your training. You will be able to discover new, more thematic subjects such as composition, portrait, night photography or Lightroom software.
1
3 Discuss with others, get inspired Try to share your love of photography throughout the year with other passionate image-makers. Photo festivals, conferences, and portfolio reviews can be good ways of making connections and building your artistic network.
2
#1 LIGHT Mode of measurement
Situation
Measured zone
Matrix or evaluative
Landscape, portrait, lowcontrast scene
The entire image
Spot
Portrait, back-lit, subject with different lighting than background
Central-weighted
Only one collimator at or outside of the centre (about 5% of the image)
When the centre of the image
The entire image, but with the
must be well exposed without
weight on the centre of the
knowing precisely where to
image
measure with the Spot mode.
Selective (only Canon)
Similar to the Spot mode but without clearly knowing precisely where to measure the light.
Identical to Spot mode, but covering a larger zone (about 10 % of the image around the chosen target)
3
Matrix
4
Spot (placed below the lamp shade)
Selective (placed below the lamp shade)
4
5
Combinations of aperture settings, speed and ISO sensitivity can give the same exposure, for example the following 3 settings will produce the same image in terms of exposure – and histogram (according to the principle of the exposure triangle).
Setting 1
Setting 2
200 ISO
100 ISO
f/4
f/4
1/400 s
1/800 s
Setting 3 ISO 100 f/2.8 1/800 s
In other words: From 1 to 2: if you double the ISO keeping your aperture constant, you will need to double the shutter speed from 1/400 s to 1/800 s to get the same exposure. From 1 to 3: If you double the shutter speed keeping the ISO constant, you will need to double the amount of light reaching the sensor by opening the aperture and going from f/4 to f/2.8 From 2 to 3: If you divide the ISO value by 2 keeping a constant shutter speed, you will need to double the amount of light reaching the sensor by opening the aperture and go from f/4 to f/2.8
6
5
#2 MANUAL FOCUSING
Nowadays and despite the omnipotence of autofocus, manual focusing may still be necessary; too little light in the subject or lack of contrast can prevent the autofocus from focusing. For manual focusing, the photographer can use: - its viewfinder (but very tight on an APS-C) - the distance graduation on the focus ring (on some lenses only) - the digital zoom and live view (very precise solution, but requires stability)
7
8
#3 AUTOFOCUS, HOW DOES IT WORK? The autofocus system analyzes the contrast of the subject to be focused; knowing that the more blurred an element is, the less contrast it has, the autofocus adjusts its distance value until it achieves optimal contrast of the subject, and therefore its sharpest focus. The autofocus system therefore requires a sufficiently bright scene to be able to “see� and analyze the contrast of its subject. The autofocus can focus at various points in the image (frame) by means of collimators, represented by small squares visible in the viewfinder, that are in fact the representation of the electronic cells used to make the autofocus. There are three types: - Vertically oriented collimators - Horizontally oriented collimators - The cross/square collimators (they are placed in the centre of the frame and are the most efficient, as they adapt to all the orientations of the subject).
9
10
#4 DIFFERENT AUTOFOCUS MODES Mode
How it works
Use cases
OneShot / AF-S
It will focus when the shutter-re-
Static subjects
lease button is pressed.
(portrait, architecture,...)
The focus is confirmed.
Can be used with: - Only one collimator, which can be placed in the frame.
Servo / AF-C
It will continually adjust its focus
Subjects in motion (foot-
according to the movement of the
ball player, dancer, sing-
subject.
er,...)
This mode never confirms the focus.
Ai Focus / AF-A
It will automatically switch from
- A group of collimators, which is possible to move within the frame. - All the collimators.
Static and mobile subjects
OneShot/Af-S to Servo/AF- C mode if it detects movement of the subject.
AF-S works most often, but when the subject is in a strong position and you have a shallow depth of field, the probability of missing focus in AF-S is such that you need to switch to Servo..
11
#5 MANUAL MODE This mode of capture is indicated by the “M” pictogram.
12
It allows the adjustment of the three exposure factors (aperture, shutter speed and sensitivity). A gauge tells us the future exposure of the scene, depending on the aperture, speed and sensitivity chosen. This gauge can be found at various points of the camera: within the viewfinder, on the small upper control panel (on the expert and professional camera), and on the back of the camera.
13
Notes
14
GLOSSARY OF PHOTOGRAPHIC TERMS A
especially toward the edges of the frame. Chro-
Autofocus:
pensive lenses, although even the best optics
matic aberration is most common on less exA system of sensors and motors that
can occasionally display lower levels of chro-
allow lenses to obtain focus automatically; in
matic aberration under certain conditions.
some cameras, the system also allows the lens
D
to maintain focus on a moving subject. Autofocus can be Continuous, meaning focus is maintained regardless of where it moves
Depth of field:
within the frame, or Single, meaning the point
of focus is locked regardless of where the sub-
appears to be in focus and will be reproduced
ject may move.
as being acceptably sharp in an image. Depth
The range of distance in a scene that
of field is controlled in particular by the lens
B
aperture, and extends for a distance in front of and behind the point on which the lens is fo-
Backlight:
When the light source is behind the
subject.
entering the camera. An adjustable diaphragm enlarges or reduces the size of the hole, or A device for measuring the light to ad-
just the exposure of a camera. Collimator: The collimator shows the area of the
image where the distance is set (in an autofocus system) for focusing. It may also be used for light measuring in case of “spot’ measuring mode.
aperture permitting more or less light to pass through the lens to the film or digital sensor.
E EXIF (Exchangeable Image File):
Data produced by a digital camera that
is attached to each image made by that camera (including information about the model of the camera, various settings, time stamping, etc).
Chromatic Aberration:
A ring or plate with a hole in the centre,
the size of which controls the amount of light
Cell:
Diaphragm or aperture:
C
cused.
Colour fringing that occurs when a
lens does not focus different wavelengths (colours) of light equally. The results of chromatic aberration (green or purple generally) are most noticeable around the edges of high-contrast images,
Exposure:
It is the phenomenon of light striking
the surface of film or digital imaging sensor. The exposure is determined by the quantity of light passing through the lens aperture (defined by the f-stop) combined with the duration of the exposure (shutter speed), hitting a sensor with a given sensibility (ISO).
15
The proper exposure, which is best determined
In 24x36 mm format a focal length of 50 mm is
by the light-metering cell, can be established
considered a normal lens, a focal length less
in a number of exposure modes including
than 40mm corresponds to a wide-angle lens
manual, program (automatic), shutter priority
while a focal value greater than 70mm is a
and aperture priority.
telephoto lens.
Over-exposure: a prolonged exposure resulting in too much light that can ‘wash out’ or
Focus:
erase important image details. These “burned”
zones of the images will show in pure white.
light meet after being refracted or reflected.
Underexposure: an inadequate exposure re-
(2) The focal point of a lens.
sulting in overly dark areas in the image.
(3) The clear and sharply defined con-
(1) A point at which converging rays of
dition of an image, as in “ is image is in focus.” Exposure Modes:
ting on a lens to obtain a sharply defined im-
P - Programmed Auto: the camera sets
the shutter speed and aperture for optimal ex-
(4) The adjustment of the distance set-
age, as in to focus a camera.
posure.
S or Tv - Shutter Priority / Time Value:
File format:
User chooses the shutter speed; camera se-
lects aperture for best results.
camera’s memory. JPEG, TIFF and RAW (DNG
or other proprietary le formats) are the most
A or Av - Aperture Priority / Aperture
Value : User chooses aperture; camera selects
The way an image is saved to a digital
common le formats found in digital cameras.
shutter speed for best results
M - Manual: User controls shutter
speed, aperture and ISO.
Fill-in:
The use of a flash during the day when
facing the sun so as to balance the natural Exposure time:
and artifcial light. This technique opens up the
shadows.
The exposure time is the time required
for the digital sensor or film to be properly exposed. Editing:
H
The process by which you choose the best im-
Histogram:
agery for presentation or story telling.
A graph that shows the distribution of
the tones in a digital image, ranging from black
F
(left) to white (right). A photographer can use a histogram to understand and manipulate ex-
Focal length:
It is the distance between the focal
point of a lens and the film plane when the lens is focused at infinity. It is used to designate the relative size and angle of view of a lens, expressed in millimeters (mm). A particular lens’ focal length can generally be found engraved or printed on the front of the lens.
16
posure. Many digital cameras have the ability to show the photographer a histogram of an image he or she has taken. Most image editing applications can create a histogram for an image.
I
L
Image definition:
Lens:
The definition of an image corresponds
A true “lens” is a single piece of glass
to the total amount of pixels within that image,
(or other transparent substance) having one
obtained by multiplying the amount of horizon-
or more curved surfaces used in changing the
tal pixels by the amount of vertical pixels. It is
convergence of light rays. What we common-
usually expressed in mega pixels or million of
ly call a photographic lens is more accurately
pixels. the definition will have an impact on the
and technically called an “objective,” an optical
maximum size of print of a picture.
device containing a combination of lenses that receives light rays from an object and form an
ISO:International Standards Organization (or
image on the focal plane. However, dictionar-
ASA):
ies have come to accept the usage of the term
ISO in digital photography represents
“lens” to mean the entire photographic objec-
the sensitivity of the electronic sensor that
tive itself. A photographic lens will always be
captures the image and is designated by a sin-
called a lens, even though it is not a lens, but
gle, almost universally-accepted common rat-
has a lot of lenses in it. A camera lens collects
ing system which uses the initials “ISO” before
and focuses rays of light to form an image on
the digital camera’s sensitivity setting number
a digital camera’s sensor or a traditional cam-
- e.g. ISO 100. The higher this value, the more
era’s film.
sensitive the sensor is. Light:
J
in an image.
JPEG:
Join Photographic Experts Group.
A standard for compressing image data where the size of the file is reduced. JPEG, with its 16.7 million colours, is well suited to compressing photographic images. A “JPEG” image file name carries the extension “jpg” (e.g. “portrait.jpg”). Many people refer to an image in JPEG format as a “JPEG,” pronounced “jaypeg”.
-Incident light: Light falling on a sur-
face - not the light reflected from it. Incident light rays are those that strike an object.
-Low light: The darkest zones of light in
an image. A low light zone can also be considered a shadow.
-Reflected light: The light reflected off
a subject. The camera sensor and the film pick up on this light.
M
K
Mégapixel:
Kelvin:
-High light: The most luminous zones
A unit of temperature. In photography,
it refers most often to the temperature of a colour. The visible light spectrum is scientifically described in terms of colour temperature, and
Refers to a million of pixels and is used
in describing the number of pixels that a digital device’s image sensor has. See “Image definition”.
is measured in degrees Kelvin (K).
8
17
N
colour is undiluted by white light. On an every-
Noise:
tally unsaturated colour photograph becomes
day basis, the degree of colour intensity. A toParasite pixels that distort a digital
photograph. Superimposed pixels on the image can appear distributed in a regular or irregular fashion. The intensity depends on numerous factors (sensitivity, luminosity, temperature,
Sensor:
A sensor is an electronic system that
transforms light into electronic signals. These
the size of the sensors).
signals are then converted into digital values
P
point in the image.
Abbreviation for “picture element”, a
pixel is a small square of coloured light that forms a digital image. It is the smallest unit in a digital image. Think of a pixel as a single small tile in a large mosaic.
A file format that contains the original
creates a sort of digital “negative” that must be converted into a standard format with the help of software. Resoluition: Defines the number of points per inch.
One could not say that the resolution characterizes an image, but rather its representation on a screen or a printer. Resolution also refers to the number of pixels a scanner can extract from a document.
S
sor when it is closed, and allows light to reach it when it is open. Shutters are composed of blades, a curtain, a plate or another movable cover. They control the amount of time that
TIFF (Tagged-Image File Format): This is an image format that does not degrade the image (but will occupy more disk space du to its size). It is used for optimal image resolution. Treatment :
Adjustments made to a digital photo
to change its original aspect like saturation settings, brightness, contrast, colour ... Also called “post-production”.
V Vignette:
Saturation: The saturation expresses the purity of
the colour, i.e. the absence of gray and intermediate tones. Technically, the degree to which a
traveling through the lens to the image sen-
T
metadata with no particular treatment. This data
The shutter blocks the passage of light
reach the image sensor.
RAW:
light is allowed to pass through the opening to
R
that reflect the intensity of colours for each
Shutter:
Pixel:
18
monotone—or black and white.
Vignetting is specific to zoom focal
length and aperture: light is distributed unevenly and what results is a gradual reduction of the light at the edges of the image causing dark borders.
9
W WB-auto (Automatic White Balance): This is the automatic adjustment of the white balance, ie colourimetry depending on the light source. White balance:
White balance is the way to correct the
colour matching of an image based on the type of lighting to prevent an incorrect colourcast in the image. White-angle:
A wide-angle is a lens used for short
focal lengths (less than 40mm). The angle of vision is, as the name suggests, high.
Z Zoom-Digital:
A digital zoom interpolates the central
part of the image to simulate an optical zoom. The more one zooms in on the subject the more one loses in quality in the image. Zoom-Optical:
An optical system composed of lenses
that allow you to “zoom in” or “zoom out” on your photographic subject without changing your physical position or the definition of the captured image.
19
Learn more about the work of great photographers on these topics:
Exercez votre oeil Depth of field and sharpness
1
Stefan Vanfieteren for his portraits with minimum depth of field, Ansel Adams, Edward Weston and more from the “group F / 64” for landscapes and still lifes.
2
Blur, shake and stopped action
For blur, see: Bernard Plossu, Willy Ronis (e.g. “Vendome rain”, 1947) For stopped action and movement: Cartier-Bresson and his famous decisive moment (which defines the moment the photographer presses the release button and captures a defining image.
Light and colour
3
Bruce Gilden (Flash), Martin Parr (very marked colour and circular flash) and Massimo Vitali for his famous overexposures.
20
Inspire your photography with our magazine
mag-en.thephotoacademy.com
21
Go to our PhotoWalks and share with the community of your city
rebrand.ly/photowalks
22